One means of utilizing coal today is to generate combustible gas by the incomplete combustion of the coal in a coal gasifier. A typical gasifier is comprised of two zones. In the first, heat is generated for the gasification process. In this zone, coal is burned under stoichiometric (no excess air) conditions. The hot gas generated in the first zone is used to drive off the volatiles from coal introduced to the second zone. This zone is operated with little or no air introduced thereto, so little or no combustion of the coal takes place. The gas leaving the second zone is mainly carbon monoxide. This gas also carried with it a considerable amount of char, which is separated out of the gas stream after it leaves the gasifier. This char contains a considerable amount of combustible carbon and, thus, it can be recycled back to the first zone of the gasifier for complete combustion.